In general, an airspring is a pneumatic spring configured as a column of gas confined within a container. The pressure of the confined gas, and not the structure of the container, acts as the force medium of the spring. A wide variety of sizes and configurations of airsprings are available, including sleeve-type airsprings, bellows-type airsprings, convoluted-type airsprings, rolling lobe airsprings, etc. Such airsprings commonly are used in both vehicular and industrial applications. Vehicular applications include suspension systems for automobiles, light trucks, semi-tractors and trailers, buses, trains, recreational vehicles, etc., while industrial applications include use in vibration isolation systems.
Airsprings, regardless of their size and configuration, share many common elements. In general, an airspring includes a flexible, sleeve-like member made of fabric-reinforced rubber that defines the sidewall of an inflatable container. Each end of the flexible member is closed by an enclosure element, such as a bead plate which is attached to the flexible member by crimping. The uppermost enclosure element typically also includes air supply components and mounting elements (e.g., studs, blind nuts, brackets, pins, etc.) to couple the airspring to the vehicle structure. The lowermost enclosure element also typically includes mounting elements to couple the airspring to the vehicle axle.
In vehicular applications, airspring suspensions offer many advantages over conventional steel spring-type suspension arrangements, particularly with respect to driver discomfort, cargo damage, and vehicle deterioration. For example, the principle drawback of steel spring suspension systems is their degree of stiffness. Because steel springs must be designed to handle the vehicle's maximum load, the suspension system often is too stiff to provide adequate, or any, shock absorption at light or no-load conditions. Airspring suspension systems, on the other hand, can accommodate load changes simply by adjusting the amount of air pressure in the inflatable container. Air pressure adjustments can be performed automatically via appropriate sensor and control arrangements.
However, the ability to pressure and depressurize the inflatable chamber has created a new problem unique to airspring suspensions. In particular, as air is being removed from the inflatable chamber, the top enclosure element begins to move toward the bottom enclosure element of the airspring, and the flexible sidewall of the container has a tendency to collapse inwardly on itself. Such collapse can result in pinching of the flexible material of the sidewall, which eventually can result in wear and tear, leading to perforation or other damage to the airbag.
Accordingly, it would be desirable to provide an improved airspring design which restricts inward collapse of the flexible sidewall, thus preventing damage to and prolonging the useful life of the airspring assembly. Moreover, it would be desirable to provide a method whereby the improvement can easily be added to existing airspring designs.